test(tui): isolate viewport-height remount regression

Keep the resize delta below the virtual history scroll quantum so the regression test specifically depends on viewport height entering the snapshot key.

ui-tui/src/__tests__/virtualHistoryOffsetCache.test.ts

@@ -129,7 +129,7 @@ describe('useVirtualHistory offset cache reuse', () => {
 
     try {
       await delay(20)
-      instance.rerender(React.createElement(Harness, { expose, height: 24, items, maxMounted: 80 }))
+      instance.rerender(React.createElement(Harness, { expose, height: 9, items, maxMounted: 80 }))
       await delay(80)
 
       expect(viewportIsMounted(items, expose.current!.virtualHistory, expose.current!.scroll!)).toBe(true)